Structural geology of a classic thrust belt earthquake : the 1999 Chi-Chi earthquake Taiwan ( M w Z 7 . 6 )

Abstract We document the structural context of the 1999 Chi-Chi earthquake ( M w =7.6) in western Taiwan, which is one of the best-instrumented thrust-belt earthquakes. The main surface break and large slip (3–10 m) is on two segments of the shallow otherwise aseismic bedding-parallel Chelungpu–Sanyi thrust system, which shows nearly classic ramp-flat geometry with shallow detachments (1–6 km) in the Pliocene Chinshui Shale and Mio-Pliocene Kueichulin/Tungkeng Formations. However, rupture is complex, involving at least six faults, including a previously unknown deeper thrust (8–10 km) on which the rupture began. We compare the coseismic displacements with a new 3D map of the Chelungpu–Sanyi system. The displacements are spatially and temporally heterogeneous and well correlated with discrete geometric segments of the 3D shape of the fault system. Geodetic displacement vectors are statistically parallel to the nearest adjacent fault segment and are parallel to large-scale oblique fault corrugations. The displacement magnitudes are heterogeneous at several scales, which requires in the long term other non-Chi-Chi events or significant aseismic deformation. The Chelungpu thrust has a total displacement of ∼14 km but the area of largest Chi-Chi slip (∼10 m) is on a newly propagated North Chelungpu Chinshui detachment (∼0.3 km total slip) which shows abnormally smooth rupture dynamics.

[1]  J. Suppe,et al.  Shear Fault-bend Folding , 2004 .

[2]  Jérôme Lavé,et al.  Active folding of fluvial terraces across the Siwaliks Hills, Himalayas of central Nepal , 2000 .

[3]  C. Ji,et al.  Slip distribution and tectonic implication of the 1999 Chi‐Chi, Taiwan, Earthquake , 2001 .

[4]  C. Wang,et al.  Structural mapping of the 1999 Chi-Chi earthquake fault, Taiwan by seismic reflection methods , 2002 .

[5]  D. Wells,et al.  New empirical relationships among magnitude, rupture length, rupture width, rupture area, and surface displacement , 1994, Bulletin of the Seismological Society of America.

[6]  D. Dreger,et al.  The Combined Inversion of Seismic and Geodetic Data for the Source Process of the 16 October 1999 Mw 7.1 Hector Mine, California, Earthquake , 2002 .

[7]  Geodetically Observed Surface Displacements of the 1999 Chi-Chi Earthquake near Southern Termination of the Chelungpu Fault , 2002 .

[8]  Chien‐Hsin Chang,et al.  Relocation of the 1999 Chi-Chi Earthquake in Taiwan , 2000 .

[9]  Shui-Beih Yu,et al.  GPS measurement of postseismic deformation following the 1999 Chi‐Chi, Taiwan, earthquake , 2003 .

[10]  Rémi Michel,et al.  Horizontal coseismic deformation of the 1999 Chi-Chi earthquake measured from SPOT satellite images: Implications for the seismic cycle along the western foothills of central Taiwan , 2003 .

[11]  Changjiang Wu,et al.  Source Process of the Chi-Chi Earthquake: A Joint Inversion of Strong Motion Data and Global Positioning System Data with a Multifault Model , 2004 .

[12]  C. Wang,et al.  Constructing subsurface structures of the Chelungpu fault to investigate mechanisms leading to abnormally large ruptures during the 1999 Chi‐Chi earthquake, Taiwan , 2004 .

[13]  T. Seno.  THE INSTANTANEOUS ROTATION VECTOR OF THE PHILIPPINE SEA PLATE RELATIVE TO THE EURASIAN PLATE , 1977 .

[14]  Zhenxing Yao,et al.  Complexity of the coseismic rupture for 1999 Chi-Chi Earthquake (Taiwan) from inversion of GPS observations , 2004 .

[15]  J. Suppe.  Tectonics of arc-continent collision on both sides of the South China Sea: Taiwan and Mindoro , 1988 .

[16]  Paul Segall,et al.  Imaging the ramp-decollement geometry of the Chelungpu fault using coseismic GPS displacements from the 1999 Chi-Chi, Taiwan earthquake , 2004 .

[17]  C. Wang.  Detection of a recent earthquake fault by the shallow reflection seismic method , 2002 .

[18]  C. DAVISON,et al.  The Seismological Society of America , 1915, Nature.

[19]  Tzay-Chyn Shin,et al.  The Chi‐Chi, Taiwan earthquake: Large surface displacements on an inland thrust fault , 1999 .

[20]  Shui-Beih Yu,et al.  Spatial and Temporal Distribution of Slip for the 1999 Chi-Chi, Taiwan, Earthquake , 2004 .

[21]  Chien-Hsin Chang,et al.  An Interpretation of the 1999 Chi-Chi Earthquake in Taiwan Based on the Thin-Skinned Thrust Model , 2000 .

[22]  H. Kao,et al.  Active detachment of Taiwan illuminated by small earthquakes and its control of first-order topography , 2002 .

[23]  Y. Hsu,et al.  Preseismic deformation and coseismic displacements associated With the 1999 Chi-Chi, Taiwan, Earthquake , 2004 .

[24]  J. Suppe.  Principles of structural geology , 1984 .

[25]  M. Takeo,et al.  Determination of constitutive relations of fault slip based on seismic wave analysis , 1997 .

[26]  J. Suppe.  Kinematics of arc-continent collision, flipping of subduction, and back-arc spreading near Taiwan , 1984 .

[27]  S. Mitra.  Three-dimensional geometry and kinematic evolution of the Pine Mountain thrust system, southern Appalachians , 1988 .

[28]  Manuel G. Bonilla,et al.  A review of recently active faults in Taiwan , 1975 .

[29]  J. Rundle,et al.  The growth of geological structures by repeated earthquakes, 1, conceptual framework , 1988 .

[30]  P. Segall,et al.  The co-seismic slip distribution of the Landers earthquake , 1994, Bulletin of the Seismological Society of America.

[31]  Semih Ergintav,et al.  Time-Dependent Distributed Afterslip on and Deep below the İzmit Earthquake Rupture , 2002 .

[32]  S. Stein,et al.  A model for the motion of the Philippine Sea Plate consistent with NUVEL‐1 and geological data , 1993 .

[33]  Oceanside and Thirtymile Bank blind thrusts: Implications for earthquake hazards in coastal southern California , 2000 .

[34]  M. Sambridge,et al.  On entropy and clustering in earthquake hypocentre distributions , 2000 .

[35]  S. Hartzell,et al.  Comparison of L1 and L2 norms in a teleseismic waveform inversion for the slip history of the Loma Prieta, California, earthquake , 1991 .

[36]  N. Hirata,et al.  Aftershock Observations of the 1999 Chi-Chi, Taiwan Earthquake , 2000 .

[37]  J. Suppe,et al.  Mechanics of fold‐and‐thrust belts and accretionary wedges: Cohesive Coulomb Theory , 1984 .

[38]  Robert S. Yeats,et al.  The geology of earthquakes , 1997 .

[39]  J. Shaw,et al.  Estimation of fault propagation distance from fold shape: Implications for earthquake hazard assessment , 2000 .

[40]  W. Witherspoon,et al.  Palinspastic map of East Tennessee , 1978 .

[41]  Xavier Le Pichon,et al.  Seismic cycle in Taiwan derived from GPS measurements , 2001 .

[42]  H. Kao,et al.  Exactly Where Does the 1999 Chi-Chi Earthquake in Taiwan Nucleate?-Hypocenter Relocation Using the Master Station Method , 2000 .

[43]  Jyr-Ching Hu,et al.  Geometry and structure of northern surface ruptures of the 1999 Mw=7.6 Chi-Chi Taiwan earthquake: influence from inherited fold belt structures , 2002 .

[44]  J. Chow,et al.  Shallow Reflection Seismics Aiding Geological Drilling into the Chelungpu Fault After the 1999 Chi-Chi Earthquake, Taiwan. , 2002 .

[45]  H. Kanamori,et al.  Elastohydrodynamic lubrication of faults , 2001 .

[46]  H. Kao,et al.  Source Parameters of Regional Earthquakes in Taiwan: 1999-2000 Including the Chi-Chi Earthquake Sequence , 2002 .

[47]  Teh-Ru Alex Song,et al.  Spatial slip distribution of the September 20, 1999, Chi‐Chi, Taiwan, Earthquake (MW7.6) —Inverted from teleseismic data , 2000 .

[48]  J. Rundle,et al.  The Growth of Geological Structures by Repeated Earthquakes 2. Field Examples of Continental Dip‐Slip Faults , 1988 .

[49]  Paul Segall,et al.  Rapid afterslip following the 1999 Chi‐Chi, Taiwan Earthquake , 2002 .

[50]  R. A. Price.  An evaluation of models for the kinematic evolution of thrust and fold belts: structural analysis of a transverse fault zone in the Front Ranges of the Canadian Rockies north of Banff, Alberta , 2001 .

[51]  Paul Segall,et al.  Fault geometry and slip distribution of the 1999 Chi‐Chi, Taiwan Earthquake imaged from inversion of GPS data , 2001 .

[52]  Jeen‐Hwa Wang,et al.  Conjugate thrust faulting associated with the 1999 Chi‐Chi, Taiwan, earthquake sequence , 2002 .

[53]  H. Kanamori,et al.  Evidence for fault lubrication during the 1999 Chi‐Chi, Taiwan, earthquake (Mw7.6) , 2003 .

[54]  Shui-Beih Yu,et al.  Velocity field of GPS stations in the Taiwan area , 1997 .

[55]  C. Ji,et al.  Slip history and dynamic implications of the 1999 Chi‐Chi, Taiwan, earthquake , 2003 .

[56]  Yuehua Zeng,et al.  Fault Rupture Process of the 20 September 1999 Chi-Chi, Taiwan, Earthquake , 2004 .

[57]  Shearer,et al.  An elusive blind-thrust fault beneath metropolitan los angeles , 1999, Science.

[58]  G. King,et al.  Seismic Potential Revealed by Surface Folding: 1983 Coalinga, California, Earthquake , 1984, Science.

[59]  H. Yen,et al.  Mapping the northern portion of the Chelungpu fault, Taiwan by shallow reflection seismics , 2002 .

[60]  P. Jordan,et al.  Hangingwall geometry of overthrusts emanating from ductile decollements , 1992 .

[61]  J. Suppe,et al.  Three-dimensional imaging of active structures using earthquake aftershocks: the Northridge thrust, California , 2002 .

[62]  C. Wang,et al.  Investigating Near-Surface Structures Under the Changhua Fault, West-Central Taiwan by the Reflection Seismic Method , 2003 .

[63]  Yuan-Hsi Lee,et al.  Slip vectors of the surface rupture of the 1999 Chi-Chi earthquake, western Taiwan , 2003 .

[64]  Hugo Perfettini,et al.  Postseismic relaxation driven by brittle creep: A possible mechanism to reconcile geodetic measurements and the decay rate of aftershocks, application to the Chi-Chi earthquake, Taiwan , 2004 .

[65]  Xavier Le Pichon,et al.  Coseismic slip resolution and post-seismic relaxation time of the 1999 Chi-Chi, Taiwan, earthquake as constrained by geological observations, geodetic measurements and seismicity , 2004 .